This invention relates to internal combustion engines, and in particular, to an improved throttle structure for controlling the passage of fuel to the combustion chambers of the engine, and for mixing and modulating liquid fuel and intake air in order to reduce undesirable exhaust emissions from such engines.
In combustion engines prevalent today, the combustion chambers of the engine are connected to a source of fuel and a source of air through an intake manifold and a carburetor. The carburetor has a main air passageway extending through it, and a venturi restriction is used to draw fuel into the air stream. Control of the flow through the passageway is obtained through the use of a throttle valve. Throttle valves used in the prior art conventionally have been a butterfly valve-type device.
It long has been known that the combustion chambers of an engine receive varying amounts of fuel during operation of the engine. Ideally, each intake stroke of the piston should draw a fuel-air mixture into a particular combustion chamber which would burn completely during the power stroke of the piston. Unfortunately, fuel/air distribution does not match the ideal. The reasons for unequal distribution also generally are known. Thus, when the fuel/air mixture strikes a conventional throttle valve, large droplets of fuel often are formed. Large fuel droplets do not move readily through the intake manifold to the combustion chambers, and distort the fuel/air ratio when they do arrive. In addition, the throttle valve commonly is pivotally mounted across the diameter of the carburetor passage. Fuel/air movement past the throttle is unbalanced or directed toward one side or the other of the passageway by the very presence of the throttle valve. Although some mixing of the two air streams imposed by the throttle valve does occur below the throttle valve, the assymetrical distribution of the fuel and the intake air rarely is overcome completely.
A number of attempts have been made to improve the consistency of the air/fuel mixture delivered to the cylinders of internal combustion engines. In general, prior art attempts involve complicated redesigns of the fuel/air delivery system, for example, by the use of fuel injection mechanisms, or complicated redesigns of the engine. While such systems and designs work for their intended purposes, they are expensive to produce initially and often are expensive to maintain in normal operation and use.
An example of an improved throttle structure with which the invention disclosed hereinafter is compatible is disclosed in a co-pending application by James T. Bickhaus, "Throttle Structure for an Internal Combustion Engine," Ser. No. 727,713, filed 9/29/76. An invention dealing with subject matter related to that described herein is described in a co-pending application by Edward H. Casey, "Means for Imparting Supersonic Flow Characteristics in the Intake Manifold of an Internal Combustion Engine," Ser. No. 727,719, filed 9/29/76. Both applications are assigned to the assignee of the present invention. Information disclosed in these co-pending applications is intended to be incorporated by reference.
The invention disclosed herein provides an improved throttle means for a conventional carburetor, which accomplishes sonic flow with simplified structure. As described more fully hereinafter, the incoming fuel and air mixture, in one embodiment of the invention, is permitted to strike the bottom wall of the intake manifold of the engine. A throttle means, which generally is similar to that described in the above-referenced Bickhaus application, Ser. No. 727,713, filed 9/29/76, as modified by this invention, is utilized to regulate engine demand with fluid flow. The throttle means and intake manifold are arranged so that fluid flow through the throttle passes through a restriction for obtaining sonic flow, and a diverging portion which imparts supersonic and then subsonic flow to the mixture.
Devices and methods for obtaining supersonic flow in internal combustion engines also are known in the art. For example, the Eversole, U.S. Pat. No. 3,778,038, issued Dec. 11, 1973, describes a particular approach to obtaining supersonic flow in the intake supply system of an engine.
In distinction to prior art designs, this invention accomplishes supersonic flow with little modification either to the conventional carburetor structure or to the conventional intake manifold.
One of the objects of this invention is to provide a throttle structure for an internal combustion engine which gives better fuel/air mixture distribution to the cylinders of the engine.
Another object of this invention is to provide a throttle valve structure having an inlet side and an outlet side, the outlet side being positioned in the inlet manifold of an internal combustion engine.
Another object of this invention is to provide a throttle valve structure which utilizes a tubular body member as the valve element.
Another object of this invention is to provide a throttle valve structure which imparts supersonic flow to the fuel mixture passing through it.
Yet another object of this invention is to provide a throttle structure imparting supersonic flow characteristics to the fluid mixture passing through it without requiring major design changes in either the carburetor or the intake manifold of the engine.
Still another object of this invention is to provide a cylindrical throttle valve structure having an end modified to provide sonic flow to a fuel/air mixture.
Other objects of this invention will be apparent to those skilled in the art in light of the following description and accompanying drawings.